The unapprehended major risks to human health associated with carbon dioxide breathing toxicity related to climate change.

Carbon dioxide gas is toxic to humans. While the dangerous effects of breathing high levels of CO2 are well known, there has been little attention to the lower levels that, with continuing emissions, will soon pervade our environment. From short-term exposure studies, there are known health effects at only ten times the current ambient atmospheric concentration of carbon dioxide. Although longer term exposure studies are scarce, there is evidence that the actual safe level of carbon dioxide for breathing is much lower when considering a lifetime exposure. The possibility exists that before the end of this century, carbon dioxide levels will be such that the human lifespan will be significantly shortened due to the failure of the body's compensatory mechanisms under long-term exposure. As such there is a credible risk of approaching extinction of many species including humans.